1. Field of the Invention
This invention generally relates to an image forming apparatus such as a copying machine or the like, and more particularly, to an image forming apparatus having a function to obtain a combined image from a plurality of documents.
2. Description of Related Art
As one example of performances executed by a copying machine, there is an editing work, whereby necessary parts are extracted from a plurality of documents thereby to edit one image. Editing becomes necessary to obtain a combined image, for instance, when the using copying machine is equipped with various kinds of optional functions. Conventionally, in such case as above to obtain the combined image, copies of images from a plurality of documents are cut and bonded on a board sheet, or a desired image is extracted in a combining mode.
However, it takes much trouble to copy the documents once, cut and bond the copied images on the board sheet and then copy the board sheet again, resulting in a long time of work and degradation of the image quality every time copying is performed.
On the other hand, editing according to the combining mode can prevent degradation of the image quality, but requires additional devices corresponding to the desired image. The manipulation of the apparatus becomes therefore complicated. At the same time, the structure and cost of the apparatus is increased. For example, an editor and a combining device are necessitated to effect the combining mode in a general mono-color copying machine. The editor is used to take out necessary parts of the document by inputting coordinates of four points in a scanning direction of the document and in a direction orthogonal to the scanning direction and taking out an image of the part enclosed by the four points or the part except the enclosed part. It is troublesome to input the coordinates. The combining device circulates a paper to which an image is once transferred and fixed so as to transfer another image again to the paper. The combining device becomes inevitably bulky in structure. Moreover, although a full-color copying machine using an intermediate transfer body does not require the combining device since a combined image can be formed on the intermediate transfer body, the editor is indispensable to take out the necessary image, thereby giving rise to the same problems as described above.